This invention relates to the swaging of preferably a square tube.
In the past, others have tried to swage tubes, in order to reduce their dimensions, and normally this could be done through the use of an external compression means, that would apply pressure around the periphery of the tube, to decrees its dimensional capacity. Normally this was done with round tubes, which could be carefully pressured by some type of dies or roller means around its circumference, and which would affect the reduction in its diameter, to a slight amount, without causing a buckling of the round tube itself.
But, others have tried to swage a rectangular tube, utilizing the same principle of applying force upon the exterior surface of the tube, but generally have not succeed in their efforts, because square tubes, unlike round tubes, have a tendency to buckle along the straight sides of their configuration, when subjected to pressure along the sides, and around the corners, in an effort to reduce the tubes dimensions.
Normally, tubes are reduced in size for the purpose of allowing a series of such tubes to be connected together. If the ends of a tube can be reduced in size, it can then fit inside the next aligned tube, to make it easier to connect a series of such tubes together, where such may be required for installation purposes.
An example of a tool for working shaped, hollow metal tubing to achieve its end reduction can be seen in the published international application to Soder, International Publication No. WO 98/41338. As can be seen, it utilizes a series of rollers, which applies compressive forces along the upper and lower surfaces, and the side surfaces, of the tube being worked, as to be noted. But, generally, when such type of external compression is applied to a multi-sided tube, such as a square tube, and as to be noted in FIG. 1 of this application, the flat side portion of the tube has a tendency to buckle, as explained, which means the tube must be scraped, since it becomes inutility.
A much more substantial connecting means between tube lengths, and some of these tube lengths may be of a length of 20 to 40 feet in length, if the end of the tube is damaged because of buckling, it makes the tube unusable, and requires that end of the tube to be cut off, in an effort to try to swage a new end for the tube to make it useful: For example, some of these tubes may be approximately 24 feet long, and heretofore, when they may be assembled into, for example, a TV antenna, which may be a 100 feet tall tower, the only way to combine such tubing was to utilize a small length of tube, in which the two ends of two tubes may inset, and then be joined through bolting, or being welded in place. Another method was to use butt welding of the ends of the two adjacent tubes, or in the alternative, to use some other kind of especially designed fitting. But, these means for connection while they may hold up under short term usage, when subjected to lateral forces, such as wind, and the like, do have a tendency to break, or bend, because the means for connection is just not that stable. Hence, the desirable manner for interconnecting such tubes together is to be able to swage uniformly one end of the tube, and allow the opposite end of another tube to insert thereover, and then either weld or bolt the tubes sections together, to provide for a highly stable tubular joint connection.
In the past, commonly tubes were joined end to end by various common methods. These included the placement of one sleeve of a smaller size that fitted within the I.D. of the tubes being joined, and then were bolted or welded in place. Another method including the butt welding method and such welding is very difficult to accomplish, and to maintain structural strength, particular where thinner walled tubes were involved, and had to be joined. In addition, there are specially designed fittings that could be used for holding tubes ends together.
It has generally been recognized that it is difficult to swage a square or rectangular tube; it is rarely ever accomplished primarily because the tube surfaces have a tendency to buckle, or crimp, and therefore lose their square or rectangular integrity.
It has been know that swaging of a round tube can be accomplished. It has been done on either a segment swager or the tube is forced into a die that has the desired shaped of the tube after its fabrication. Due to the symmetric nature of the round tube, no I.D. mandrel, such as a support mechanism, normally is required. As force is apply, such as by squeezing on to the round tube, the walls want to buckle in the outward direction. But, the die doing the squeezing is there to keep that from occurring. Instead of buckling, the material compresses, thickening the wall and lengthening the tube. In cases of very thin wall thickness, and relatively large diameter of the tube, the material will find a way to buckle inwardly. This problem is generally magnified if the material is of a very high strength and resists forming.
If one attempts to use the same process on a square or rectangular tube, as done with the round tube, the wall first wants to buckle as it does with the round tube, but it does not care if it is an inward buckle or an outward buckle. Since the dies are there to stop the outward buckle, it normally goes inwardly. The buckle is inconsistent in appearance and dimensions and results in a useless part.
Thus, the concept to swager a square tube is to support the I.D. or the inside diameter of the tube, so that the walls cannot buckle inwardly. The immediate problem one encounters by placing some sort of support in the I.D. of the tube is that after the swage is complete, the finished tube is crimped tightly on the support and must be extracted with significant force. There are prior art custom built machines that have used hydraulics, to ram the tube into a die to achieve a final shape, but such machines are inconsistent of results, and they are extremely expensive to manufacture.